Small gun perforators for oil wells



- March 16, 1954 ALLEN SMALL GUN PERFORATOR FOR WELLS Filed Sept. 11, 1950 RL I. m 1 2 mm W M) m Z ,/A/Z M w M m n i T Z 6 V, Q :v 2

ATTORNEY.

Patented Mar. 16, 1954 SMALL GUN PERFORATORS F OR OIL WELLS Thomas 0. Allen, Bellaire, Tex., assignor, by

mesne assignments, to Standard Oil Development Company, Elizabeth, N. J a corporation of Delaware Application September 11, 1950, Serial No. 184,162

3 Claims.

This invention relates to guns for perforating pipe in oil wells or the like and more particularly to guns which are small enough to run through tubing in a well for perforating casing beneath the tubing.

Guns and explosives have long been used for perforating casing in oil Wells and the art is well developed. As commonly constructed the barrels of guns used for such purposes are fixed horizontally in a carriage and these barrels approach in length, as far as is practical, the diameter of the casing so as to obtain the maximum fire power. Even under the best conditions, effective perforation of oil well casing and the cement which usually surrounds it, is difiicult to accomplish, and since the siz of the gun is important, casing perforators as conventionally used have not been run into the well through tubing or other pipe smaller in diameter than the casing.

It has recently been proposed to perform certain operations including the perforating of casing in an oil well While tubing is in it. See for example application of Theodore A. Huber, Serial No. 133,025, filed December 15, 1949, for Method of Completing and Repairing Oil Wells, where the use of a casing perforating gun capable of being run through tubing is required. Large savings in time and cost can be effected in this way if effective perforation can be accomplished.

In accordance with application Ser. No. 184,161,

filed September 11, 1950, by Theodore A. Huber, now Patent No. 2,639,770, it is proposed to solve the problem of providing effective firing power to perforate casing with an assembly which is run into and out of the well through tubing by arranging the guns in their carriage on trunnions and by providing means for rotating them from the vertical positions which they occupy While being lowered into the well, into horizontal firing positions. Inasmuch as the guns may be fired by electricity, Huber proposed to employ an electric motor to rotate them exactly the right amount. In accordance with the present invention, it is proposed to provide a telescoping structure for lengthening the barrels of guns after they have been run into the well through tubing to accomplish the purposes mentioned. If trunnions are used on barrels, they take up space and limit the diameter of the barrels materially.

The guns of the present invention do not have this disadvantage. The gun may have a relatively large diameter bore and the telescoping sleeve therein may be detached therefrom when the bullet is expelled so that the carriage may be retrieved through the tubing.

The objects of the invention will be apparent from the following description, taken in connection with the accompanying drawings in which:

Fig. 1 is a vertical cross-sectional view of tubing in an oil well with a fragmentary portion of a gun constructed in accordance with the present invention located therein in the runningin position, it being understood that as many barrels as desired may be employed, all being like the one illustrated.

Fig. 2 is a vertical cross-sectional view of casing in an oil well with the gun of Fig. 1 being fired to perforate the casing and the surrounding earth formation.

Fig. 3 is a vertical enlarged cross-sectional view of the sleeve and bullet of Fig. 1.

Referring to the drawing in detail, it will be seen that an oil well casing is shown at I2. A tubing 13 is positioned in the well with its lower end above the portion of the casing which is to be perforated.

Within the tubing 13, as shown in Fig. 1, there is a gun body or carriage 14 which is lowered into the well on a cable (not shown). This carriage may be made of steel and it is of cylindrical shape with a number of sockets 16 provided transversely to accommodate gun barrels I! which are mounted on threads la in the sockets H5.

The rear or breech end of each socket l6 may be filled with powder as shown at 20 and the rear is slightly larger in diameter than along the threads is to make a sort of ring shaped powder chamber.

Within the bore of each barrel I! there is a sleeve 2! and a bullet 22. There is also a shear cup 23 surrounding the rear end of the barrel I1 and attached to the bullet 22 and there is a sealing disk 24 at the front or muzzle end of the barrel l1.

As shown in Fig. 3, the sleeve 2| is slightly shorter than the bullet 22. The bullet may be held temporarily against movement independent of the sleeve 2| by shear pins l9, as shown in Fig. 3, although with some designs, such pins may not be necessary. The arrangement should be such that the nose of the bullet 22 strikes the casing to be perforated before the sleeve 2| strikes the casing and if the relative size of tubing 13 and casing [2 permit, the nose of the bullet 22 should strike the casing just as the rear end of the sleeve 2! leaves the barrel [1.

The guns may be fired by electric fuses 25 connected to an electric conductor 26 in accordance with the usual technique.

The purpose of the telescoping sleeve 2| is to increase the effective length of the barrel I! while 3 the bullet 22 is being projected therefrom and while it is traveling from the gun body It to the casing l2. The expanding gases resulting from the explosion are largely confined within the barrel and sleeve until the bullet strikes the easing. Thus their driving force is not wasted, as would largely be the case if the sleeve were not present. Thus, it will be apparent from the foregoing description taken with the drawing that the bullet is slidably arranged within the sleeve and the sleeve and bullet are inter-connected by the shear pins I9, the sleeve being open at each end with the rear ends of the sleeve and bullet being even with each other. As the powder in the powder chamber burns gases are formed which drive the bullet and sleeve assembly from the gun barrel. The assembly strikes the casing or target causing the shear pin to shear allowing the bullet to penetrate or perforate the cas ing. Thus, the sleeve is momentarily held against Y the casing on impact and serves to guide the bullet and confine the gases from the powder chamber for a sufficient length of time to drive the bullet into the formation to be penetrated. Thus where the space between the opening in the gun barrel and the wall of the casing is substantially equal to the length of the sleeve, the gun barrel is effectively lengthened by the sleeve travelling with the bullet, the sleeve acting and serving the function of an extension to the gun barrel. The sleeve both confines the gases and guides the bullet.

When the sleeve 2| strikes the casing it stops, as shown in Fig. 2 and then falls down free from the barrel 1! as shown in dotted lines. tive areas of sleeve and bullet exposed to the explosive pressure and other ballistic factors should preferably be such that only sufiicient force is imparted to the sleeve 2| to cause the sleeve to travel along with bullet 22 until the bullet strikes the casing and pins 19 are sheared.

While only one embodiment of the invention has been shown and described herein, it is obvious that changes may be made without departing from the spirit of the invention or the scope of the annexed claims.

I claim:

1. A device adapted to be arranged in a tubing gun barrel which comprises, a bullet. a sleeve having first and second open ends slidably arranged around the bullet to travel with the bullet on leaving the gun barrel on firing the gun, said The rela- 3 sleeve being arranged around the bullet to extend with its second open end even with the rear end of the bullet, and at least one shear pin connecting the bullet and sleeve for travel with the bullet until the bullet and sleeve strike a target to free the bullet from the sleeve through the first open end of the sleeve on shearing the shear pin and thereby increase the effective length of the gun barrel while the bullet travels from the gun barrel to the target.

2. In an arrangement for perforating casing in oil wells and the like, an elongated tubular body small enough in diameter to enable it to be run into the well through tubing inside the casing to be perforated, sockets in said body and gun barrels mounted in said sockets, each barrel having a bullet therein adapted, when projected from the gun barrel to perforate the casing, each bullet having a sleeve having first and second open ends slidably arranged around the bullet to travel with the bullet on leaving the gun barrel on firing the gun, said sleeve being arranged around the bullet to extend with its second open end even with the rear end of the bullet, and at least one shear pin connecting the bullet and sleeve for travel with the bullet until the bullet and sleeve strike the casing to free the bullet from the sleeve through the first open end of the sleeve on shearing the shear pin and thereby increase the effective length of the gun barrel while the bullet travels from the gun barrel to the casing.

3. The arrangement defined in claim 2 in which the sleeve is slightly shorter than the bullet so that the bullet strikes the casing before the sleeve does so.

THOMAS 'O. ALLEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re. 1,787 Smith Oct. 4, 1864 Re. 1,788 Smith Oct. 4, 1864 21,924 Gibbs Oct. 26, 1858 42,268 Boekel Apr. 12, 1864 2,306,140 Reed Dec. 22, 1942 2,334,931 Johnson Nov. 23, 1943 OTHER REFERENCES Ser. No. 276,093, Schlumberger (A. P. C.), published May 4, 1943. 

